The invention relates to a fuel injection pump for internal combustion engines, in particular for Diesel engines, as defined hereinafter.
A considerable disadvantage of passenger cars equipped with Diesel engines is what is known as bucking at low rpm; bucking occurs not only at full load and partial load but also at low rpm, primarily when accelerating and decelerating, when the driving pedal is actuated quickly. Vehicle bucking is largely precluded in Diesel engines that have fuel injection pumps by equipping them also with damping devices, which allow changes in the fuel injection quantities, effected by the fuel injection pump when the driver "steps on the gas" or "lets up on the gas" quickly, to come into effect only after a delay.
In a known fuel injection pump of the above generic type (German Offenlegungsschrift 34 27 224), the hydraulic damping device is disposed between the pump rpm adjusting lever which is coupled to the driving lever, and the vehicle body; the damping cylinder is connected to the body, while the damping piston is joined via a piston rod to the rpm adjusting lever. A throttle by which two damping chambers located on opposite ends of the piston communicate is disposed in a longitudinally continuous axial bore of the damping piston. The rpm adjusting lever is mounted for rotation with a pivotable adjusting shaft in the housing of the fuel injection pump and a lever is rigidly secured on the end of this shaft that protrudes into the pump interior. The lever is engaged by the governor spring connected to the governor lever. The driving pedal engages the rpm adjusting lever via compression springs. Upon quick actuation of the driving pedal, the rpm adjusting lever follows its action only with a delay, because it is supported on the body via the damping device. With increasing torque, the engine, mounted on the body by means of resilient buffers, leans to one side about its longitudinal axis In this process, the rpm adjusting level is supported on the body via the damping device and is pivoted in the direction for reduction of the fuel injection quantity. Conversely, with rapidly decreasing torque the engine leans to the other side, and the rpm adjusting lever is displaced by the damping device in the direction of an increasing fuel quantity. The damping device thus has a delaying effect upon "stepping on the gas", and a differentiating effect when the fuel quantity is changed by the deflection of the engine. In the opposite direction, that is, upon "letting up on the gas", the damping device functions correspondingly. With the negative feedback between the engine motion and the metered fuel quantity, vehicle bucking is actively damped. However, the damping effect is always of equal magnitude during "stepping on the gas" and "letting up on the gas", so that vehicle bucking is not optimally suppressed in all cases.